This invention relates to a communications system employed in electrical distribution systems and the like; and, more particularly to an improvement in a switched-load transmitter used in such communications systems.
As discussed in provisional patent application 61/332,406, conventional transmitters installed in some electric meters are resistive load transponders. These transmitters have certain disadvantages including, for example, heat dissipation, frequency response, line interferences, and problems with the local voltage supply, as well as requiring a great deal of power in order to achieve the signal strengths needed for a communication's link.
A proposed solution to these problems, as set forth in provisional patent application 61/332,406, is to replace these transmitters with a resonating transmitter in which the resistive load is replaced with a purely reactive load having both capacitive and inductive elements. Such a transmitter, with appropriate modulation, consumes substantially less power while producing inbound signals of sufficient spectral signal strength. That is, the resonating transmitter generates pulses useful for passband communications while consuming, on average, 100 times less power than the resistive switched-load transmitters currently in use in communications networks. The signal strength produced by the resonating transmitter has been found to be comparable to that produced by conventional resistive load transmitters at the necessary frequencies. However, certain problems still remain. One of these is that the transmitter transmits only a dampened sinusoidal signal which limits the rate at which data can be transmitted over the utility's power distribution network. A second problem has to do with the relatively narrow bandwidth in which the resonant transmitter operates. It has been found that the resonant transmitter is subject to signal-to-noise (SNR) degradations due to powerful narrowband noise, this being because the transmitter is a narrowband transmitter. This degradation impacts the quality of transmissions from the transmitter and requires improvement.